Refining of petroleum hydrocarbons



Patented Jan. 3, 1928.

1,655,069 UNITED'STATE'S PATENT OFFICE.

PAUL MCMICHAEL, OF FLUSHING, NEW YORK, A SSIGNOR TO HYDROGARIBON REFINING PROCESS COMPANY, INC., OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

REFINING F PETROLEUM HYDROCARBONS.

No Drawing.

This invention relates to an improved method for refining petroleum hydrocarbons, and more particularly relates to a method for refining light petroleum oils and distillates, especially gasolinerontaining cracked oils and pressure distillates.

Light petroleum distillates, particularly those intended for use in automobile internal combustion engines, should be of good color,

free from objectionable odors, substantially free from sulfur, and from gum and resin forming constitutents. Cracked distillates usually contain a reduced amount of sulfur and an increased amount of unsaturated material. The formation of gummy and resinous masses on standing, and the instability of certain oils to prolonged exposure to light, are largely due to the presence in the oil of unsaturated material such as terpenes, diolefines, and isomers, polymers and homologues or derivatives thereof. All unsaturated compounds, however, are not objectionable in these respects, and some unsaturated compounds, such as the olefines, constitute an excellent and advantageous constituent for motor fuel, and their removal constitutes an unnecessary loss. Sulfur compounds ancl gum forming compounds are particularly objectionable in oils intended 1:0 for use in internal combustion engines because they tend to form gummy deposits in various parts of the engine and to form corrosive combustion products.

Hitherto, the general practice in the refining of such oils has involved initial treatment With sulfuric acid, and the reaction products of such initial treatment are of such character as to entail the use of strong sulfuric acid for removing them. Treatment with strong sulfuric acid substantially denudes the oil of any olcfines and similar unsaturated compounds it may have contained prior to the treatment and tends to introduce sulfur into the oil in the form of alkyl sulfates. Refining methods have also been proposed involving initial treatmentof the oil with quite dilute sulfuric. acid, but such methods, if carriedout in a manner to avoid destruction or removal of the olefines and similar compounds, do not produce a stable product of good color and odor and free from gum and resin forming bodies. Another disadvantage of those previous methods of refining with sulfuric acid which have Application filed February 14, 1924. Serial No. 692,896.

been found commercially useful has been the number of distillations involved.

In my prior applications, filed September 26th, 1923, Serial No. 665,008, October 23rd, 1923, Serial No. 670.226 and January 11, 1924, Serial No. 685,703, I have pointed out that sulfuric acid corresponding to a concentration between about and 83% H will substantially eliminate the diolefines, terpenes and similar gum and resin forming compounds but acts very slowly, if at all, upon unsaturated compounds such as the olefines, and that, with such relatively dilute sulfuric acid, the rigor of the treatment required to effect substantially complete removal of gum and resin forming bodies does not materially affect the olefines present and does not introduce sulfur into the treated oil to any objectionable extent. The refining method described in the first of these applications involves the preliminary digestion of the oil at an elevated temperature with a fixed alkali before treatment with relatively dilute sulfuric acid, the method described in the second application involves distillation in the presence of a fixed alkali after treatment with relatively dilute sulfuric acid, and that described in the third application involves treatment of the oil with relatively dilute sulfuric acid, preceded by treatment with a fixed alkali at ordinary temperature. The method of the present invention may be employed in conjunction with any of these proccsses.

I have found that petroleum oils, particularly cracked distillates, which are bad odored and tend to darken on exposure to air or sunlight and to deposit gummy or resinous material can be freed with sulfuric acid treatment of sulfur, and gum and resin forming bodies, and components that tend to impart objectionable color much more easily if such constituents have been partially oxidized. For example: 100 cc. (measured at 15 C.) of a freshly cracked petroleum distillate Were evaporated to constant Weight on a water bath in a hemispherical copper dish about 3% in diameter. The residue weighed 0.867 gms. Another portion of this same distillate was treated with 60 1345. sulfuric acid in successive portions aggregating 2.5% by volume of the oil at a temperature of 4 0 (1., and, after separation of the oil and acid, washed successively With water and a 2% solution of caustic soda and a test sample finally dried over anhydrous sodium carbonate. 100 cc. of this treated second portion were evaporated to constant weight on a water bath in a similar copper dish. The residue weighed 0.138 gms. Another portion of the same distillate, sufficient to fill a glass bottle about one-third full, was allowed to stand in the bottle in contact with the air therein and in direct sunlight for about 30 days, during which period the distillate changed in color from a very light brown to a dark red brown. This portion was then subjected to acid treatment identical with that to which the second portion was submitted, and 100 c. c. of the treated third portion evaporated to constant weight on a water bath in a hemispherical copper dish about 3% in diameter. The residue weighed 0.092 gms.

I have also found that the removal by sulfuric acid treatment of components imparting bad odor and color and tending to form gummy or resinous deposits is facilitated by precedent partial oxidization even though the amount of such constituents present, as indicated by the residue left upon evaporation, is apparently increased by such partial oxidization. For example: Two samples of 100 cc. each of the same petroleum distillate were taken and evaporated to constant weight in hemispherical copper dishes about 3 in diameter, the first over a water bath in which the water was kept boiling freely, and the second in an oven maintained at a temperature of 90 C. and under a va uum of 10 of mercury, whereby air was excluded. (The temperature of 90 C. under a 10 vacuum was substantially equivalent to the higher temperature used with the first sample at atmospheric pressure.) The residue from the first sample weighed 0.028 gins, that from the second 0.0172 gins.

According to the present invention, the oil is subjected to treatment with relatively dilute sulfuric acid. of sufiicient strength to remove substantially completely the gum and resin forming bodies present and in con-- junction with alkaline treatment to eliminate constituents imparting bad odor and color, and of insuflicient strength to remove. any substantial quantity of the olefines pres cut, and, previous to this acid treatment. the oil is subjected to treatment with a fixed alkali in the presence of air whereby a. partial oxidization of the objectionable constituents is obtained. The treatment with a fixed alkali in the presence of air may be carried out at ordinary temperatures. but it is more advantageously effected at elevated temperatures. According to this invention, the treatment of the oil with fined alkali in the presence of air may be carried out with an oxygen carrier present 1n the Oil or in contact therewith, either at ordinary temperature or at elevated temperature.

By treating the oil with a fixed alkali in the presence of air, sulfur compounds, and gum and resin forming bodies, and components tending to impart color are converted into a form in which they are much more easily removed by subsequent treatment with sulfuric acid, and, in some cases, a considerable portion of these objectionable constituents, particularly the sulfur compounds, are removed directly by the alkaline treatment. In some cases, the'climination of sulfur so closely parallels the removal of gum form ing bodies as to indicate a close relationship between these components.

For example: A petroleum distillate. lightbrown in color and containing 0.49% by weight of gum forming components and 0.125% by weight of sulfur. was treated, in

accordance with this invention, successively with by volume of a 40 B. solution of caustic soda in the presence of air and 2 /170 by volume of 60 B. sulfuric acid. After this treatment the gum forming components remaining in the distillate amounted to 0.00% by weight (a decrease of about 88%) and the sulfur content was 0.045% by weight (a decrease of about 64%) and the distillate was of good color.

To further illustrate: A portion of freshly cracked petroleum distillate, light brown in color and showing a. residue of 0.367 gms. after evaporation of 100 00., was mechanically agitated for about 3 hours at atmospheric temperature with 5% by volume of a. 40 Be. solution of caustic soda. The agitation was carried out in a closed vessel having a volume about five times that of the combined distillate treated and the treating solution, air occupying the remainder of the vessel. and, at irregular intervals during the period of agitation. agitation was stopped and the vessel opened to the atmosphere for intervals of about five minutes. The distillate was then separated from the treating solution and a portion for analysis dried over anhydrous sodium corbonatc after repeated washing witlrwater. 100 cc. of this treated distillate were evaporated to constantweight as previously described, the residue weighing 0.245 gins. This exemplifies the direct removal of objectionable compounds by the alkaline treatment in the presence of air. The treated distillate was then agitated with 2.5% by volume of 00 B. sulfuric acid at atmospheric temperature for about one hour, separated from the acid sludge, successively washed with water and a 2% solution of caustic soda. and a portion for analysis finally dried over anhydrous sodium carbonate. The distillate was of good color and 100 cc. of the treated distillate then showed a residue of 0.040 gins. upon evaporation to constant weight,

-- tion for analysis finally dried over anhydrous sodium carbonate. 100 cc. of the treated distillate were evaporated to con stant weight, as previously described, after which the residue weighed 0.290 gins. The distillate was then agitated for about 1 hour with 2.5% by volume of 60 Be. sulfuric acid, separated from the acid sludge, washed with water and then with a 2% solution of caustic soda, and a portion for analysis finally dried over anhydrous sodium carbonate. The distillate was of good color and 100 cc. of the distillate so treated after evaporation to constant weighe left a residue of 0.072 gms. v

To further illustrate: A portion of a petroleum distillate, light red brown in color having a sulfur content of 0.61% by weight, was agitated for about two hours at atmospheric temperature with 2.5% by volume.

of a B.;solution of caustic soda in a closed vessel having a volume approximately fOl-l times the combined volume of the distillate treated and the treating solution and through which air was passed, separated from the solution of caustic soda, washed with water and a portion for analysis dried over anhydrous sodium carbonate. The sulfur content of the treated distillate at this stage was 0.36% by weight. The distillate was then treated for about l hour at. a temperature of about C.. with 2.5% by volume of sulfuric acid,.separated from the acid sludge. washed with water several times.

and then with a 2% solution of causic soda, and then dried over anhydrous sodium carbonate. The sulfur content of the distillate then was 0.058% by weight.

By effecting the treatment with alkali in the presence of air at an elevated temperature, a better, and sometimes a quicker, refining action is obtained. and the treatment so carried out is particularly advantageous where it can be combined with a distilling operation. The. treatment may be effected .bv digestion at elevated temperature in a closed vessel or by digestion with a reflux condenser of sufiicient capacity to prevent loss of the lighter partof the distillate. The digestion is advantageously carried out at or above'the boiling point of water where a water solution or emulsion of the fixed alkali is employed. lVhere the alkaline treatment of the invention is carried out in combination with a distilling operation, air, which may be heated or unheated, may ad vantageously be introduced through the oil undergoing distillation. Steam may likewise be employed during distillation and its use is advantageous where the refined prodnot will not be subjected to further rcdistillation.

For example: A portion of a petroleum distillate, light brown in color and showing a residue of 0.367 gins, after evaporation of 100. cc.. cited in a preceding example, was introduced into a still, together with 5% by volume of a 40 B. solution of cars tic soda and approximately 100% by volume of fresh water, and wholly distilled therefrom with steam and air. The mixture of petroleum vapors and steam was condensed and collected, the excess air passing through the receiver. The water and distillate were separated and a portion of the distillate dried over anhydrous sodium carbonate for analysis. 10000. of the distillate so treated were evaporated to constant weight, as previously described, after which the residue in the copper dish weighed 0.135 gms. The distillate was then treated at atmospheric temperature for about 1 hour with 2.5% by volume of B. sulfuric acid, separated from the acid sludge, successively washed with several portions of water and then with a 2% solution of caustic soda, and a portion for analysis finally dried over anhydrous sodium carbonate. The distillate was then water white and left a residue of 0.020 gins. after evaporation of cc. to constant weight.

As a further example: A portion of a freshly distilled petroleum oil, having a sulfur content of 1.52% by weight. was refluxed with an emulsion of calcium hydroxide for a period of three hours. The weight of lime employed was about 2% hv ,weight of the distillate and the volume of the distillate and the emulsion were approximately equal. Suflicient condensing surface was provided so that the water could be boiled 'without any of the distillate being lost. After the digestion, the oil and the emulsion were separated, and the oil washed. and a test sample dried over anhydrou sodium carbonate. The sulfur content of the oil then was 0.513% by weight.

,To further illustrate: Two portions of a petroleum distillate which had a light brown color and a distinct odor of hydrogen sulfide were separately distilled with about an equal volume of water and 2.5% by volume of a 40 Be. solution of caustic soda. The first distillation was carried out with steam alone and the second with steam and air. in both cases the gases being introduced below the surface of the aqueous layer in the still. The distillates were collected. separated from water and test samples were dried over anhydrous sodium carbonate. The first showed a discoloration with a doctor soluihl tion after standing minutes. The second was water white and did not show any discoloration after standing overnight with a doctor solution, although it did blacken after about 15 minutes when shaken with flowers of sulfur and a doctor solution.

The modification of the sulfur compounds,

and gum and resin forming bodies present in certain petroleum oils and distillates to forms in which they are more readily removed by subsequent treatment with sulfuric acid is further expedited by effecting the partial oxidation with air in the presence of a fixed alkali together with an oxygen car= rier. The hydrates of the metals of variable valence which are capable of acting as oxidizing or reducing agents are suitable oxygen carriers. The hydrates of chromium, cobalt, copper, iron, manganese and nickel, for example, may be employed. These hydrates are advantageously introduced in a low state of oxidation, and may conveniently be brought into contact with the oil by adding a salt of one of these metals, preferably in alower state ofoxidation, to the alkaline treating solution or emulsion, and providing sufficient excess alkali therein. It is to be noted that these oxygen carriers act in the nature of catalysts rather than as oxidizing agents. Oxygen carriers which are also adapted to form compounds with andremove sulfur in the form of certain compounds that occur in some oils, such as the hydrates above mentioned, are particularly useful since they serve a double function.

The treatment with a fixed allzali and an oxygen carrier in the presence of air may be carried out at atmospheric temperature but is more advantageously effected at elevated temperature.

For examplez'A portion of a petroleum distillate, light red brown in color and showing a residue of 0.420 gms., cited in a preceding example, was agitated with air for about two hours at atmospheric temperature with 2.5% by volume of a 10 B. solution of caustic soda to which approximately 1% by volume of a saturated solution of ferrous.

sulfate had been added. The ferrous sulfate was introduced aftertheoil and alkaline solution had been placed in the agitator, the

separated from the acid sludge, washed with water and then with a 2% solution of caustic soda, and a portion for analysis finally dried over anhydrous sodium carbonate. 100 cc. of the treated distillate were then evaporated to constant weight leaving a residue of 0.028 gms.

To further exemplify the invention-- another portion of the distillatetreated in the preceding example was introduced into a still together with 2.5% by volume of a 40 B. caustic soda solution, 1% by volume of a saturated solution of ferrous sulfate and i tion for analysis dried over anhydrous so-- dium carbonate. 100 cc. of the distillate, which was water white, left a residue of 0.011 gms. after evaporation to constant weight. c

To further illustrate: A portion of a petroleum distillate, light red brown in color and with" a sulfur content of 0.61% by weight, cited in a preceding example, were agitated for about two hours at atmospheric temperature with 2.5% by volume of a 40 B. solution of caustic soda and 1%. by volume of a. saturated solution of ferrous sulfate. After agitation"= was concluded, the sludge, including principally iron hydroxide and iron sulfide, was allowed to settle and the oil separated from the caustic ,solution and the sludge. 'Iheipil was then Washed and a portion for analysis was dried over anhydrous sodium carbonate. The sulfur content of the distillate so treated was 0.20% by weight. After agitation forl hour at atmospheric temperature with 2.5% by volume of 60 B. sulfuric acid, and washing and drying of the oil after separation from the acid sludge, the sulfur content was 0.02; by weight.

As a further example: Another portion of the distillate treated in the preceding example was introduced into a still together with 2.5% by volume of a 40 B, solution of caustic soda, 1% by volume of a saturated solution of ferrous sulfate and about 100% by volume of fresh water, and wholly distilled therefrom. After separation and drying of the distilled oil, it had a sulfur content-of 0.031% by weight. After agitation for 1 hour at atmospheric temperature with 2.5% by volume of 60 B. sulfuric acid, and washing and drying of the oil after separation from the acid sludge,- the sulfur con- Zoo tent was imponderable, sulfur being present,

if at all, only as a faint trace.

As a further illustration: A petroleum distillate, having a light brown color and a distinct odor of hydrogen sulfide, cited in a previous example, was distilled with steam and air in the presence of 2.5% by volume of a 40 Be. solution of caustic soda, 1% by volume of a saturated solution of ferrous sulfate and 100% b volume of fresh water. The separated an washed distillate was Water white and did not show any discoloration after standing 48 hours with a doctor solution and required more than 30 minutes "to show any indication of sulfur when shaken with flowers of sulfur and a doctor solution.

The alkaline treatment of the present invention is particularly advantageous in conjunction with subsequent treatment with relatively dilute sulfuric acid since it ren ders the objectionable constituents of the hydrocarbons being refined much more susceptible to the action of the dilute acid.

- This makes the combined operation more efiic'acious and also tends to reduce the time and amount of acid required in acid treatment. The method of the present invention, for the same reasons, is particularly advantageous when employed in conjunction with the methods described in the prior applications heretofore referred to.

The total amount of sulfuric acid employed and the total time of agitation of the oil with the sulfuric acid depends upon the degree of concentration of the acid employed and the composition of the oil being treated. Advantageously the total quantity of acid may be divided into several portions and the oil treated successively with these several portions. Using from 1.5% to 15% of the weight of the oil of sulfuric acid of a specific gravity of 60 B., the total time of agitation may aggregate from 1 to at hours. Following separation of the oil and acid after acid treatment, the oil may be washed with water to remove excess acid and this wash may be supplemented with a mild alkaline wash'to complete the removal of acid. One of the characteristics of the refined products of the invention is the agreeable odor which they possess. The odor suggests isopropyl or isobutyl alcohol. Repeated washing with warm water eliminates this odor from the oil, leaving the usual hydrocarbon odor, but carries it into the wash water. I Treatment with strong sulfuric acid likewise removes this odor. The refined products of the invention are furthermore of good color and odor, substantially free from gum and resin forming components, stable to prolonged exposure to air or sunlight and likewise contain substantially all of the olefines and similar unsaturated hydrocarbons originally present,

earth metal hydroxide, in the presence of air, for example, can be very effectively carried out in the ordinary air agitator. One

of the principal advantages of the present invention is the small number of operations required to produce a completely refined hydrocarbon product.

In treating relatively low boiling hydro carbons, for example an oil distilling 85% below 225 C., it is advantageous to treat the oil at ordinary temperature-with a fixed alkali in the presence of air, with or without an oxygen carrier, then to subject it to treatment with relatively dilute sulfuric acid at" ordinary temperature, and finally to distill it, with steam in the presence of a fixed alkali, accomplishing any desired fractionation during this final distillation. In treating an oil of higher boiling range, for example an oil distilling below 225 (1, and including the desired final fraction together with heavier or lighter products, it is advantageous to distill the oil with steam and air in the presence of a fixed alkali, with or without an oxygen carrier, separating any desired fraction during this distillation, and then treating it with relatively dilute sulfuric acid. In this case, the oil may be given a final alkaline wash.

As an example of the first procedure: A petroleum distillate, which had a specific gravity at,15 C. of 52 B., a gum con tent of 0.50% by weight and a sulfur content of 0.15% by weight and which distilled 79% up to 225 0., was agitated with air over a period of about three hours at atmospheric temperature with 5% by volume of a 40 B'. caustic soda solution and 1% by volume of a saturated solution of ferrous sulfate. After this treatment the distillate was separated from the alkali and sludge, washed with several successive portions of water, and, after separation from the final portion of wash water, was agitated at a temperature between about 45 and 50 C. with an aggregate of 2.5% by volume of sulfuric acid having a specific grav ty of 60 B. at 15 C. in three successive portions of 1% and 1%, over a" total period of about three hours. This acid treatment was carried out in a closed vessel to minimize losses due to evaporation and the distillate was cooled after agitation wlth each of the successive portions of acid and before separation therefrom. Following the acid treatment, the distillate was washed twice by about 10% by volume of fresh water and once with about 10%by volume of a 2% solution of a caustic soda. The loss at this point in the treatment, including all mechanical, chemical and. evaporation losses, was 3.2% by volume. T he gum forming components, determined by evaporation of 100 cc., amounted to 0.045% by weight, and the sulfur content was 0.029% by weight. The acid treated distillate was then distilled with steam in the presence of about an equal volume of a 2% solution of caustic soda. Approximately 82% by volume was distilled off and constituted the refined product. This distillate was water white (a small portion showed no discoloration after exposure to direct sunlight for three months), was sweet smelling, the odor suggesting that of isopropyl alcohol, successfully withstood the doctor test with flowers of sulfur, had a sulfur content, if any, that was imponderable, and had a content of gum forming components, determined by evaporation of 100 cc., of 0.013% by weight.

As an example of the second procedure: A petroleum distillate, which had a specific gravity of 46 B. at 15 C., a gum-content of 0.85% by weight and a sulfur content of 0.25% by weight, and which distilled 63% by volume up to 225 (1, was introduced into a still together with an equal volume of water, about 5% by volume of a 40 Be. caustic soda solution and about 1% by volume of a saturated solution of ferrous sulfate. Approximately 67% by volume of the oil was then distilled off with a mixture of air and steam, the air and steam mixture being introduced into the still below the surface of the aqueous layer therein. The separated oil distillate was then agitated in a closed vessel at a temperature of about C. over a total period of about three hours with successive portions aggregating about 2.5% by volume of sulfuric acid having a specific gravity at 15 C. of

' B. After the-acid treatment, the distillate was washed with two successive portions of water aggregating approximately 50% by volume of the distillate, and, finally, after separation from the last portion of wash water, was washed with approximately 10% by volume of a 2% solution of caustic soda. The final thus obtained amounted to approximately 64.8% by volume of the original distillate prod uct treated. The refined distillate was water white small portion exposed to direct sunlight for one month showed no discoloration at the end of that period), was sweet smelling, the odor being suggestive of isopropyl alcohol, successfully withstood the doctor test with flowers of sulfur,

had a sulfur content, if any, that was not ponderable, and had a content of gum forming components determined by evaporation of 100 cc., of 0.0033% by weight.

While several examples have been employed to articularly describe the invention, it will be understood that they illustrate the invention but that the invention is not limited thereto.

I claim:

1. A method of refining petroleum oils and distillates, which comprises subjecting the oil to treatment with a fixed alkali and ferrous hydrate in the pressence of air and thereafter subjecting the oil to treatment with from about 1.5 to 15% of sulfuric acid of a concentration between about 70% and 83% H 80...

2. A method of refining relatively low boiling petroleum oils and distillates, Which comprises subjecting the oil to treatment with a fixed alkali in the presence of air at ordinary temperature, separating the treated oil and subjecting it to treatment with from about 1.5 to 15% of sulfuric acid of a concentration between about 70% and 83% H 50 and thereafter distilling the oil with steam in the presence of a fixed alkali.

3. A method of refining relatively low boiling petroleum oils and distillates, which comprises subjecting the oil to treatment with a fixed alkali and an oxidation catalyst in the presence of air at ordinary temperature, separating the treated oil and subjecting it'to treatment with from about 1.5 to 15% of sulfuric acid of a concentration between about 70% and 83% H and thereafter distilling the oil with steam in the presence of a fixed alkali. V

In testimony whereof I affix my signaturc.

PAUL McMICHAEL. 

